Charlotte E. Moore (1898-1990), a physicist who gained international acclaim for her analysis of solar and atomic spectra, worked in the atomic physics division of the National Bureau of Standards for over twenty years. In this capacity, she supervised the compilation of numerous solar spectroscopic tables containing analytic information about the chemical and physical properties of the elemental gases comprising the sun and the solar atmosphere.
Moore received worldwide recognition for her analytic interpretations and compilations of solar and stellar spectra, including the honor of being among six women to receive the first Federal Woman's Award from the United States Government in 1961 for her outstanding contributions in a federal career. She was also the first woman scientist elected as a foreign associate, in 1949, into the Royal Astronomical Society of London.
Moore was born on September 24, 1898, in Ercildoun, Pennsylvania, to George Winfield Moore, superintendent of the Chester County Schools, and Elizabeth Palmer (Walton) Moore, a school teacher. Her parents, through their occupations and Quaker following, instilled a disciplined appreciation for learning that Moore maintained throughout her life. Upon graduating from high school in 1916, she entered Swarthmore College, graduating in 1920 with a bachelor's degree in mathematics and membership in Phi Beta Kappa. John A. Miller, Moore's physics professor at Swarthmore, was influential in her decision to pursue a career in physics.
Moore's mathematical inclinations landed her a position in mathematical computation at the Princeton University Observatory in 1920. There, she worked with the astrophysicist Henry Norris Russell, whose research had resulted in a theory of stellar evolution. Typical of most astrophysicists, Moore and Russell used spectroscopy to measure certain cosmological objects' spectra or distribution of radiation at particular wavelengths of light. By determining the wavelength at which certain spectral lines appeared, they identified the elements making up the object under investigation. Russell guided Moore's initial research into atomic spectra, and in 1928 they collaborated on the publication of a monograph on the solar spectrum of elemental iron.
Although Moore's academic astrophysics career began and would later end at Princeton, she spent eight years researching in California. For five years she worked with Dr. Charles E. St. John at the renowned Mt. Wilson Observatory in Pasadena. Their spectroscopical researches resulted in a 1928 revision of Henry Rowland's classic Preliminary Table of Solar Spectrum Wavelengths published between 1893 and 1896. This work, together with her previous research, earned Moore the Lick fellowship as she pursued doctoral studies at the University of California at Berkeley. She wrote her dissertation on the atomic lines in the sunspot spectrum and received her degree in 1931.
Upon completing her doctorate, Moore returned to the Princeton University Observatory as a researcher and remained until 1945. While at Princeton, she met astronomer and physicist Bancroft Walker Sitterly; they were married on May 30, 1937. Moore had established her scientific career and received recognition under her maiden name, so she continued publishing many journal articles under that name throughout her life, although a few publications appear under the name Sitterly or Moore-Sitterly.
Moore left the academic surrounds of Princeton and joined the National Bureau of Standards (now the National Institute of Standards and Technology) in Washington, D.C., in 1945. Joining William F. Meggers's section on spectroscopy, Moore was soon placed in charge of a project involving the compilation of data on atomic energy levels. According to her colleague William C. Martin, who authored her obituary for Physics Today, Moore regarded her position as much more than the gatherer of previously published data. She scrutinized the data and sought to correct any shortcomings by persuading spectroscopists to provide new analyses. The voluminous amount of unpublished data Moore received attested, Martin claimed, to the spectroscopists' great confidence in Moore's competence. The chief result of her stringent and persistent efforts in collecting data was the publication in 1949, 1952, and 1958 of the three-volume reference source Atomic Energy Levels as Derived from the Analyses of Optical Spectra containing an organized representation of the atomic energy information for 485 atomic species and described by Martin as "one of the most highly respected and frequently cited sources of basic atomic data ever published." While at the Bureau of Standards, Moore published other valuable reference sources including The Masses of the Stars in 1940 with Russell, her previous Princeton colleague, and The Solar Spectrum in 1947 with Harold D. Babcock. In the following decade, Moore began collaborations with Richard Tousey at the Naval Research Laboratory which were to continue until her death, using data gathered from V-2 rockets to analyze ultraviolet solar spectra. Also among Moore's accomplishments was her discovery of the existence of technetium in the sun; technetium is a highly unstable element which naturally occurs only at trace levels on earth.
In 1968, Moore officially retired from the Bureau of Standards. Her career, however, was hardly finished. She spent the next three years working at the Office of Standard Reference Data, then joined Tousey's group working at the Space Science Division of the Naval Research Laboratory from 1971 to 1978. Throughout this time, Moore retained strong working relationships with her previous colleagues at the National Bureau of Standards. She also increased her involvement in professional astronomical societies. Among those in which she held leadership positions were the American Association for the Advancement of Science, American Astronomical Society, and International Astronomical Union. Moore was the recipient of the Annie Jump Cannon prize of the American Astronomical Society in 1937 and the William F. Meggers award of the Optical Society of America in 1972; her alma mater, Swarthmore College, recognized Moore with an honorary doctorate degree in 1962, as did Germany's University of Kiel in 1968 and the University of Michigan in 1971. Moore died of heart failure in her Washington, D.C., home on March 3, 1990.
Minnaert, M., "Forty Years of Solar Spectroscopy," in The Solar Spectrum, edited by C. de Jager, D. Reidel, 1966, pp. 3-25.
Martin, William C., "Charlotte Moore Sitterly," in Physics Today, April, 1991, pp. 128, 130. □